The embodiments described herein relate to solenoid systems and methods for determining solenoid stroke, and more particularly, to a solenoid assembly and control system configured to determine the solenoid stroke based on the solenoid current profile.
Known solenoid assemblies are used in a variety of different applications. For example, known solenoid pumps are used in a variety of vehicle applications, such as, for example, to transfer oil, fuel and/or other fluids to facilitate the operation of the vehicle.
Solenoid pumps can be configured to receive an electrical current to cause an armature to move, thus actuating a pumping mechanism to enable transfer of fluid. In most known systems, the armature can be moved along a fixed stroke length, wherein the distance between two end-stops is fixed. Similarly stated, in normal operation, when the solenoid is actuated, the armature moves a fixed distance or “stroke.” An actuator rod can be coupled to the armature such that movement of the armature results in a corresponding movement of the actuator rod, which actuates the pumping mechanism (e.g., reciprocating pump). Known control systems coupled to solenoid pumps include a driver that is actuated for a predetermined duration or “pulse width,” and at a desired frequency to produce the desired pump flow rate, pressure or the like. For example, some known solenoid oil pumps operate with a pulse width of between about 50 msec and about 500 msec and at a frequency of between about 0.1 Hz and 10 Hz.
In certain circumstances, the armature and actuating rod may not travel the full stroke when the solenoid is actuated. For example, differences in properties of fluids pumped (e.g., viscosity) can result in less than full travel of the armature and actuating rod when the solenoid is energized. Similarly, changes in environment (e.g., ambient temperature) can result in less than full travel of the armature and/or the actuating rod. For example, an oil pump that is pumping higher viscosity oil during start-up conditions at cold temperatures may not experience full travel or stroke of the armature.
Failure to travel through full stroke can result in lower than desired fluid flow and/or pressure. In certain situations, this can result in damage to vehicle. For example, low oil flow can result in insufficient lubrication of key engine components, thus increasing the likelihood of engine failure. Therefore, the detection of solenoid stroke can be important to ensure proper system operation. Accordingly, some known systems are configured to detect the position of the armature and/or the actual stroke traveled during operation using position sensors. Some known systems employ mechanical switches to determine the distance traveled by the armature during operation. Such known systems, however, are expensive, cumbersome and require additional hardware.
Thus, a need exists for an improved and easy-to-implement system and method to determine a solenoid stroke.